Nowadays, biometric authentication devices for performing personal authentication by using biometric information such as a fingerprint, a vein, an iris of an eyeball, or the like are widely used. Such biometric authentication devices are broadly classified as either a one-to-one method or a one-to-N method on the basis of the number of pieces of enrolled data to be compared. The one-to-one method is a method for using another personal identification means in addition to biometric information when personal authentication is performed. The personal authentication is performed, for example, by also using an input of a user ID, an input of identification information from an IC card, or the like. In contrast, the one-to-N method is a method for performing personal authentication by using only biometric information.
With the above described one-to-N method, the personal authentication is performed on the basis of a determination threshold value for a preset degree of similarity of biometric information. Namely, the personal authentication is performed by comparing, with the above described determination threshold value, the degree of similarity obtained by making a comparison between biometric information obtained from a user and preregistered biometric information. As described above, the one-to-N method is very convenient for users since an input of information other than biometric information is not needed. However, the one-to-N method needs a process for a comparison of the degree of similarity for all pieces of registered biometric information to be identified. Accordingly, a load imposed on a biometric authentication device is high, and also the length of time needed for the personal authentication increases.
Therefore, a process is executed for reducing the number of pieces of biometric information, for which the personal authentication is to be performed, by executing a classification process for input biometric information before the process for the comparison with registered biometric information to be identified is executed. For example, if the biometric information is a fingerprint, the fingerprint is classified on the basis of input fingerprint information, and an identification target is narrowed down. By narrowing down an identification target in this way, the number of pieces of biometric information for which the identification process is to be executed is reduced, thereby lightening the load imposed on the biometric authentication device. However, attempting to narrow down the identification target sometimes fails. In this case, a binning error occurs such that the identification target is narrowed down as a classification that does not include biometric information of the target person.
Accordingly, an invention is disclosed for reducing occurrences of a binning error by putting a physiological feature into an index on the basis of biometric information such as an obtained fingerprint or the like, by classifying, for example, the number of end points of the fingerprint and the number of bifurcation points of the fingerprint respectively as index values, and by registering target fingerprint information to both classifications when a classification based on the fingerprint information when being registered is in a boundary area (Patent Document 1).
Additionally, an invention is disclosed for executing an identification process by targeting fingerprint information of all classifications if the degree of certainty of an obtained classification class is low in a method for narrowing down an identification target on the basis of a fingerprint classification (Patent Document 2).
Furthermore, an invention is disclosed for creating a fingerprint image that increases the amount of information, such as of a minutia or the like, and that enables a successful matching to be made by prompting a re-input of fingerprint information and by executing a process for merging with the re-input fingerprint information when the quality of obtained fingerprint information is low (Patent Document 3).